sanjay gupta and drew pinsky, about what medical science has learned about the mind of a killer. we'll also look ahead of where do we go from here? especially when it comes to the right to bear arms in the united states, and what president obama called the nation's epidemic of gun violence. we want to welcome our viewers in the united states and around the world. i'm wolf blitzer. we begin our special edition of "the situation room" by focusing in on the search for answers. why? why would a 20-year-old man kill his mother, then gun down 20 children and six adults at the sandy hook elementary school before taking his own life? why? police are not the only ones pouring over the evidence, exploring answers. medical investigators are all over this case as well. let's go to our chief medical correspondent dr. sanjay gupta. he is joining us now. now, sanjay, you have been taking a very close look, potentially at the mind of a killer. >> yeah, and that question, why, wolf that you ask, it is hard to say for sure whether there is ever going to be a satisfactory answer to that. but there